AC Power Cord Wire Gauge
This may have something to do with the larger conductor size in PCs. Don't know for sure though. While everything in the quote from Shunyata sounds correct to me, it's dealing with effects at rf frequencies, which I don't think would be a function of gauge per se (at least among the gauges we have been discussing). Regards, -- Al |
Al, Risch's post on AA was from Nov 2000. Lot has been learned since then regarding the effects a power cord can have on a piece of audio equipment. This may have something to do with the larger conductor size in PCs. Don't know for sure though. Question: There is a tremendous amount of electrical interference and EMI coming from outside the home that we need to protect our equipment from. This implies that we need some sort of power conditioner or filter to protect the equipment.Quote taken from shunyata info . |
Check out what this EE has to say about power cords.Interesting writeup, Jea. Thanks for calling it to our attention. Pretty much all of it rings true to me. And I think that he really manages to get across the notion that the perspectives most of us (both EE's and non-EE's) tend to bring to these issues are overly simplistic. And he provides some good insight into why stock power cords can be usually, or at least often, be expected to underperform. He does not, by the way, address in any explicit way the issue of the benefits or lack thereof of using a power cord that is heavier gauge than the wiring inside the walls. Putting aside his extensive technical verbiage, I would summarize his main points as follows: Most house wiring is either 12 gauge or 14 gauge, while many OEM cords are 18 or at best, 16 gauge. Most OEM cords do not have shielding or any provision for reducing radiated EM fields, do not have premium AC outlet plugs or premium IEC plugs for better electrical contact at these junctions.... Regards, -- Al |
One conversion I read is that 15 amps X 120 = 1,800 watts.True in simple terms but there are other factors that come into play. Depending on the type and load placed on the branch circuit can effect the total amount of power, watts/VA that may be available. Just one example would be the voltage drop on the branch circuit caused by the amount of load placed on it. Using your your formula amps X volts if the voltage drop on the branch circuit was say 5 volts then the total available power, watts, would be 15 amps X 115 volts = 1725 watts. Again in simple terms. So, the first question is: If you plug a surge protector/power strip/power conditioner into one outlet in the duplex receptacle and then plug, say, four audio components into that "power strip" can they draw the full complement of AC power available..........?Yes, provided no other loads are connected to the same branch circuit. If you plug another component into the other outlet does it reduce the power available to the "power strip"?The branch circuit ampacity rating is determined by the overcurrent device, breaker in this case, feeding the branch circuit. If the breaker is working properly when a continuous load reaches the breaker handle rating the breaker should trip open. Key word should. Depending on the branch circuit wire size, # 14awg is the minimum size for a 15 amp branch circuit, and the total length of the branch circuit wire plus the total connected load will determine the voltage drop on the line. In other words if the branch circuit length is long, as a continuous load of say 15 amps is approached the voltage drop could be sufficient to effect the sonics of your audio system.... Again in simple terms. Some food for thought, in the case of a power amp, the load placed on the AC line can be fluctuating depending on the dynamic demand that is being placed on the amp. You could very well have spikes well above the 15 amp rating of the branch circuit breaker. Simple terms? Throw in inductance, capacitance, harmonics, and what ever else that may be thrown into the mix and the whole thing changes. =================== Check out what this EE has to say about power cords. Some of Jon's explanations can also be extended to the size of the conductor, wire, used for a branch circuit run when it comes to voltage drop on the line due to the load placed upon it by the power supply/s of audio equipment. |
Increased resistance in the house wiring, due to smaller gauge or greater length, will produce a voltage loss just as readily as in the power cord. And in fact most likely to an even greater degree (since the combined current draws of multiple devices are likely to be flowing through it, rather than the current draw of just one device, and voltage drop equals current times resistance). Probably why many advocate dedicated circuits. I would start with dedicated circuits, as short a run as possible from the panel, then an adequate gauge power cord (the same gauge or larger than the romex) that is as short as practical. |
And my basic point, I guess, is that having no explanation is far preferable to having an incorrect one. Because the incorrect perspective that can result from an incorrect explanation can negate the value that good science and engineering CAN bring to the table.Al, I'm down with that! And I'm a big fan of the physicist Richard Feynman, who has said many times that he's comfortable knowing there are things he can't know ;-) Punch him up on You Tube. But some people just HAVE to have an answer, even if it's a bit of a fairy tale. (I think they call it religion or something ;-) In any case, so far, I've not found anyone who couldn't hear a consistent improvement (in their amplifiers that is) using larger conductors. Other components, maybe not so much (except DACs as I mentioned.) But I do share your basic position, even though unlike Dr. Feynman, most folks won't be able to live with it. Neil |
Nsgarch, I take no position on your findings that "the effect of using larger (and larger!) gauge conductors is the same, regardless of the brand or topology of the cord." I have no reason to doubt that your sonic perceptions were accurate, although I'm sure that there are many others whose listening experiences and perceptions would both support and contradict your conclusions. I would certainly keep open the possibility that there are as yet unidentified design characteristics among audiophile-oriented power cords that tend to correlate with gauge, that might SEEM to produce a correlation between gauge and performance. Obviously science and engineering certainly cannot, at this point, explain everything about why we hear (or think we hear) what we hear. But they can explain a lot of things. And my basic point, I guess, is that having no explanation is far preferable to having an incorrect one. Because the incorrect perspective that can result from an incorrect explanation can negate the value that good science and engineering CAN bring to the table. Best for the holidays and new year! -- Al |
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Al -- your explanation represents sound engineering, and I know it well; in fact some embrace those principals to the point of hardwiring their amps' power supply right back to the panel, convinced that strategy will provide the very best energy transfer. Good for them;-) A real scientist would not be so sure. The facts are a little different than you imply: As I said earlier, there may be subtle reasons why subtle sonic differences may result when 10 gauge power cords are hooked into 12 gauge house wiring, but the differences are not due to the gauge per se.First, the difference is NOT subtle (you should try it ;-) Second, the effect of using larger (and larger!) gauge conductors is the same, regardless of the brand or topology of the cord -- the sonics of the amp will "open up" dramatically! In my own experiments, this improvement continued incrementally up to 8 AWG which is as far as I went, but PS Audio (I think) makes 6AWG PC's, which might make sense to some ;-) So, counterintuitive or not, it IS the gauge. Why? Well maybe Quantum physics will explain it one day ;-) I'm certainly willing to accept my own explanation as flawed (from an ENGINEERING standpoint) but it's the best I can conjure until science discovers the REAL reason. It's just a matter of time, I'm sure. . |
The age-old question, "Why make PC's any bigger gauge than what's in the wall?" has a very simple answer: 'energy transfer' I'll explain: At the risk of starting an ecclesiastical controversy (which I hope will not occur), I must respectfully but completely disagree, because as an electrical engineer I believe the quoted perspective would be severely misleading to the original poster and to others who may read this. Simply put, there is no basis whatsoever in science or engineering for viewing the ac outlet as a point of demarcation between a reservoir, and a set of tubes or whatever that draws water (or in this case current and power) from the reservoir. The wiring system is just that, a system. Energy is being transferred back and forth at a 60Hz frequency through the house wiring just as much as through the power cord. Increased resistance in the house wiring, due to smaller gauge or greater length, will produce a voltage loss just as readily as in the power cord. And in fact most likely to an even greater degree (since the combined current draws of multiple devices are likely to be flowing through it, rather than the current draw of just one device, and voltage drop equals current times resistance). As I said earlier, there may be subtle reasons why subtle sonic differences may result when 10 gauge power cords are hooked into 12 gauge house wiring, but the differences are not due to the gauge per se. Regards, -- Al |
Let's do the math. Take a stereo 100 W/ch amplifier, running in class A at 40% efficiency. That adds up to 500W draw. Much less than the 14Ga, 115V*15A=1725W capacity of the house circuit. Class A/B is more efficient and will draw varying current although most peak demand is supplied through power supply capacitors. Class D at twice the efficiency as class A, even if it had no capacitive reserve, would still be capable of 1725*80% = 690 W/ch (stereo) peaks. Unfortunately, real life doesn't work so simply and I typically suggest not exceeding 50% the rating on most electrical for audio, if possible. Consider, just for fun. my current system capable of drawing over 4000W and the electrical requirements. |
The national electrical code requires minimum AWG 12 for 15A circuits. If you're going to put in new ded. cts, for your audio, and the receptacles will be more than 20 feet from the panel, i recommend going up to AWG 10 to make up for slight voltage drop as the runs get longer. Tvad, you're not imagining things. The age-old question, "Why make PC's any bigger gauge than what's in the wall?" has a very simple answer: 'energy transfer' I'll explain: When you plug your whatever into a wall receptacle, you are basically hooking it up (in parallel with other devices plugged into that same 'branch' circuit) across two buss wires (hot and neutral) coming from the panel. Think of this buss (usually a long length of Rom-ex in the wall) as a reservoir of water that under most conditions can never be emptied. Think of the power cord as a pair of tubes (hot conductor and neutral conductor) that you stick into this reservoir. Now water can flow (current) into one conductor, through the whatever, and back out the other conductor (and this process reverses 60 times a second because the current alternates.) If the water is flowing through an amplifier, it's doing quite a bit of work, but in just a sixtieth of a second, it has to get back to the reservoir and then reverse direction! Sounds like an electron traffic jam waiting to turn into gridlock! To insure this doesn't occur, you provide many many lanes (or in this case, large conductors) and you lay them out so drivers aren't blinded by oncoming headlights (inductance and capacitance) slowing things down unnecessarily ;-) Simply put, the energy transfer requirements, back and forth between the device and the reservoir, are quite different in nature than what it takes to keep the reservoir full. Devices requiring less power (preamps, tuners) can transfer current back and forth through smaller conductors without "impediments" arising -- with one bizarre exception: DACs! (or any device with a D/A or A/D chip in it.) Don't ask me why, I don't know, but they benefit from big AC conductors also (but probably for different reasons than amps.) . |
You can see by the statement you quoted that I am not scientific enough to posit an intelligent response ... On the contrary, I sincerely felt that your entire response was quite intelligent. In that particular part of it, you were simply citing what you believe some others believe, and I have no doubt that is true (that some others have that belief). I was just saying that that belief that others may have is, in my opinion, not correct! All the best, -- Al |
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Tvad, I would like to add that I'm finding - being a newcomer - that there are many very smart individuals on this site, whether they have electrical engineering backgrounds or not. Thank you both for answering my questions. I think I now know much more about electricity - at least this area - than before. All the best for the holidays, Ken. |
Some very smart individuals with electrical engineering backgrounds will make compelling arguments in favor of using the same gauge wire in power cords as that which is in your walls because from an engineering standpoint it makes sense to do so. It will be very difficult if not impossible to fault their position. Tvad -- I have an electrical engineering background, and some people consider me to be very smart :), but I for one do not make that argument, and do not see why "from an engineering standpoint it makes sense to do so." Best, -- Al |
Re question 1: Assuming the house was wired properly, the only constraint for what is connected to a 15 amp branch served by a 15 amp breaker is that the total current drawn by all devices that are plugged into all outlets on that branch, and all devices such as overhead light fixtures that may be wired to that branch directly, should be less than 15 amps. So, yes, if you plug additional components into the other outlet the power that would be available to the strip would be reduced correspondingly. Re question 2: The current drawn through the component power cord is determined by the internal design of that component, with minor variation depending on the exact line voltage. As long as the house wiring and the power cord are of sufficient gauge to conduct that amount of current, meaning that they have low enough resistance to prevent significant voltage drop in the wiring and power cord themselves, there will be no difference in the power supplied to the component either way. If some listeners are able to perceive a slight sonic difference between the two cords, it will not be because of the difference in gauge (provided, as I say, that the gauges of both the house wiring and the power cord are adequate for the current draw of the component(s)). Regards, -- Al |
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